Clashes erupted shortly after several thousand demonstrators gathered at Alexandria's Qaed Ibrahim Mosque Friday to "defend [Islamic] scholars and mosques," and to call for Sharia (Islamic law).
After two hours of street battles, the vicinity of the mosque was mostly cleared for a while before confrontations broke out once again in surrounding streets. Several vehicles were set on fire.
The rally, which was initially peaceful after Friday noon prayers, turned violent when clashes broke out between Islamist demonstrators and rival opposition group.
According to media reports, clashes seem to have been kicked off after opposition protesters picked a fight with one of the Islamist demonstrators.
Central Security Forces (CSF), who were heavily deployed early Friday near the rallying point as a pre-emptive measure against possible violence, worked to restore order and keep both camps away from each other.
Rounds of teargas were repeatedly fired into the crowds, forcing people onto the Corniche near the mosque.
Tens of fire engines and ambulances were situated in the area, according to Al-Ahram's Arabic-language news website.
The health ministry released an initial injury toll of 32. More are expected to have been injured as the confrontations continued for hours afterwards. State news agency MENA confirmed that people from both sides have been injured.
Al-Ahram's Arabic site reported that the by dusk, Islamist protesters were forced to hide inside the nearby Miri Hospital after being chased by their opponents, who tried to follow them but were bombarded by CSF with teargas.
Meanwhile, other Islamists came from the Corniche, seeking to support their colleges but were stopped by CSF who are still unable to contain the situation.
Before violence marred the occasion, organizers of the Islamist rally set up stages and were leading religious chants. Checkpoints were also set up around the rally to search protesters before joining.
"The people want the implementation of God's Sharia," the crowds say, "we sacrifice our soul and our blood for Islam."
The protest comes after iconic Alexandria Sheikh Ahmed El-Mahalawy was held captive inside the mosque for 14 hours last Friday by worshippers angered by the overt Islamist rhetoric in his sermon.
El-Mahalawy demanded worshippers seek the implementation of Sharia (Islamic law) ahead of the referendum's first round, which was regarded as a call to vote 'Yes' for the constitution.
Over 20 people were injured last Friday in the ensuing confrontations and a few vehicles were set alight.
The Islamist forces blamed the liberal Constitution Party, headed by opposition figure and former IAEA chief, Mohamed ElBaradei, and former presidential candidate Hamdeen Sabbahi's opposition platform, the Egyptian Popular Current, for spearheading the attacks on the mosque.
The Muslim Brotherhood and the Salafist Calling, along with their respective political wings, the Freedom and Justice Party and the Nour Party, announced their participation in today's demonstration alongside other Islamist groups.
The Brotherhood statement reads that the rally would be in "response to the attacks by the militias of the Popular Current and the Constitution Party on the Qaed Ibrahim Mosque, which kept Sheikh El-Mahalawy under siege for more than 14 hours inside the mosque, and the attempts to assault more than 100 worshippers, including women and children."
The ageing El-Mahalawy also delivered this Friday's sermon, reiterating that his supporters are capable of protecting the mosque but would rather state authorities do the job.
The 87-year-old stated that last weekend's "assailants are actually the victims of those who pay people to sow discord, they are the real criminals… the same people also wanted to postpone the referendum."
The second and final phase of the constitutional referendum takes place on Saturday, when the remaining 17 governorates will take to the polls.
The first phase of the referendum saw around 57 per cent vote in favour of the contentious national charter, according to unofficial results.